50s Christmas Scene Plastic Cup Ornaments

In the 1950's my mom and a friend made Christmas ornaments using small, clear plastic cups. They glued items in the cups, then melted them in the oven. The result was a mini Christmas scene inside the melted cup. Are there specific instructions for this project?

I have an ornament that someone gave me that sound similiar. It is in a small clear plastic cup (smaller than 1 oz size) with a scene inside. But I dont remember the melting part of it. It has a cardboard bottom I think.

I might have to do a little experimenting with melting some. I can always use plastic glasses, they are real convenient when the grandkids are here. My guess is that melting them would give them an interesting free-form shape. Am I right on that?

Items such as cotton (for snow) and mini Christmas items like trees, snowmen, etc. were glued into the bottom of the cup, facing up. When heated in the oven, the sides of the cup sort of curved inward and around the items. The result looked like a scene in a clear, rounded ornament. A hole was probably positioned in the plastic over the top of the scene so it could be hung up. No two were alike in the way they heated. I'm just not sure about heating temperatures and times and recommended materials for using inside the cups.